Non-linear optical spectroscopy may be utilized to detect the presence of, to identify, and/or to visualize, one or more materials and/or objects on a surface. However, the spatial resolution of such non-linear optical spectroscopy techniques generally is limited by the diffraction limit as governed by the wavelength of light and/or the Nyquist sampling theorem. This diffraction limit is on the order of 1 micrometer, and it may be desirable to visualize objects that are several orders of magnitude smaller (e.g., on the order of 1 nm).
Detecting, identifying, and/or visualizing objects significantly smaller than 1 micrometer generally requires that electron-scattering techniques be utilized. However, electron-scattering techniques must be performed in ultrahigh vacuum environments, thus limiting their utility for many industrial applications. As an example, it may be costly, time-consuming, and/or simply not feasible to establish an ultrahigh vacuum environment around certain objects, thereby precluding scanning of these objects via electron-scattering techniques. In addition, electrons may alter the physical state of the surface instead of being purely, or largely, diagnostic in nature.
Alternatively, and in certain systems, such as biological systems, a photoactivatable label, or tag, may be added to known locations within an object to be visualized. In such a configuration, the photoactivatable label may be “turned on” or “turned off,” thereby providing additional contrast between the object to be visualized and the background, or noise, that inherently is present, preventing bleeding and/or contamination between adjacent elements of the object, and/or reducing signal aliasing. While such photoactivatable labels may improve resolution in certain systems, they may be difficult to add to and/or may contaminate other systems.
As discussed above, known systems and methods for detecting, identifying, and/or visualizing objects on a surface may not be amenable to all systems. Thus there exists a need for improved surface sensing systems and methods for imaging a scanned surface of a sample.